Modern mobile telecommunications standards continue to demand increasingly greater rates of data exchange (data rates). One way to increase the data rate of a mobile device is through the use of carrier aggregation. Carrier aggregation allows a single mobile device to aggregate bandwidth across one or more operating bands in the wireless spectrum. The increased bandwidth achieved as a result of carrier aggregation allows a mobile device to obtain higher data rates than have previously been available.
FIG. 1 shows a table describing a number of wireless communication operating bands in the wireless spectrum. One or more of the operating bands may be used, for example, in a Code Division Multiple Access (CDMA), Global System for Mobile Communications (GSM), Long Term Evolution (LTE), or LTE-advanced equipped mobile device. The first column indicates the operating band number for each one of the operating bands. The second and third columns indicate the uplink and downlink frequency bands for each one of the operating bands, respectively. Finally, the fourth column indicates the duplex mode of each one of the operating bands. In non-carrier aggregation configurations, a mobile device will generally communicate using a single portion of the uplink or downlink frequency bands within a single operating band. In carrier aggregation applications, however, a mobile device may aggregate bandwidth across a single operating band or multiple operating bands in order to increase the data rate of the device.
FIG. 2A shows a diagram representing a conventional, non-carrier aggregation configuration for a mobile device. In this conventional configuration, a mobile device communicates using a single portion of the wireless spectrum 10 within a single operating band 12. Under the conventional approach, the data rate of the mobile device is constrained by the limited available bandwidth.
FIGS. 2B-2D show diagrams representing a variety of carrier aggregation configurations for a mobile device. FIG. 2B shows an example of contiguous intra-band carrier aggregation, in which the aggregated portions of the wireless spectrum 14A and 14B are located directly adjacent to one another and are in the same operating band 16. FIG. 2C shows an example of non-contiguous intra-band carrier aggregation, in which the aggregated portions of the wireless spectrum 18A and 18B are located within the same operating band 20, but are not directly adjacent to one another. Finally, FIG. 2D shows an example of inter-band carrier aggregation, in which the aggregated portions of the wireless spectrum 22A and 22B are located in different operating bands 24 and 26. A modern mobile device should be capable of supporting each one of the previously described carrier aggregation configurations.
FIG. 3 shows conventional front end circuitry 30 for a wireless communications system capable of operating in one or more carrier aggregation configurations. The conventional front end circuitry 30 includes a first antenna 32A, a second antenna 32B, a first diplexer 34A, a second diplexer 34B, front end switching circuitry 36, filtering circuitry 38, and transceiver circuitry 40. The transceiver circuitry 40 includes a first transceiver module 42A, a second transceiver module 42B, a first receiver module 44A, and a second receiver module 44B. As will be appreciated by those of ordinary skill in the art, the first transceiver module 42A and the first receiver module 44A may each be associated with a first operating band (hereinafter referred to as band A), such that the first transceiver module 42A is configured to support the transmission and reception of signals about band A, and the first receiver module 44A is configured to support the reception of signals about band A. Similarly, the second transceiver module 42B and the second receiver module 44B may each be associated with a second operating band (hereinafter referred to as band B), such that the second transceiver module 42B is configured to support the transmission and reception of signals about band B, and the second receiver module 44B is configured to support the reception of signals about band B.
The first transceiver module 42A includes a first power amplifier 46 and a first low noise amplifier (LNA) 48. The first transceiver module 42A is configured to receive band A baseband transmit signals at a band A transmit node TX_A, amplify the band A baseband transmit signals to a level appropriate for transmission from the first antenna 32A or the second antenna 32B using the first power amplifier 46, and deliver the amplified band A transmit signals to the front end switching circuitry 36 through the filtering circuitry 38. The first transceiver module 42A is further configured to receive band A receive signals at the first LNA 48 through the filtering circuitry 38, amplify the band A receive signals using the first LNA 48, and deliver the amplified band A receive signals to a band A receive node RX_A for further processing, for example, by the baseband circuitry (not shown).
Similar to the first transceiver module 42A, the second transceiver module 42B includes a second power amplifier 50 and a second LNA 52. The second transceiver module 42B is configured to receive band B baseband transmit signals at a band B transmit node TX_B, amplify the band B baseband transmit signals to a level appropriate for transmission from one of the first antenna 32A and the second antenna 32B using the second power amplifier 50, and deliver the amplified band B transmit signals to the front end switching circuitry 36 through the filtering circuitry 38. The second transceiver module 42B is further configured to receive band B receive signals at the second LNA 52 through the filtering circuitry 38, amplify the band B receive signals using the second LNA 52, and deliver the amplified band B receive signals to a band B receive node RX_B for further processing, for example, by baseband circuitry (not shown).
As discussed above, the conventional front end circuitry 30 is configured to operate in one or more carrier aggregation modes of operation. Accordingly, the first receiver module 44A, the second receiver module 44B, and the filtering circuitry 38 are provided. The first receiver module 44A includes a first receiver LNA 54. The first receiver module 44A is configured to receive band A receive signals from the front end switching circuitry 36 at the first receiver LNA 54 through the filtering circuitry 38, amplify the band A receive signals using the first receiver LNA 54, and deliver the amplified band A receive signals to a second band A receive node RX_A1 for further processing, for example, by baseband circuitry (not shown). Similarly, the second receiver module 44B includes a second receiver LNA 56. The second receiver module 44B is configured to receive band B receive signals from the front end switching circuitry 36 at the second receiver LNA 56 through the filtering circuitry 38, amplify the band B receive signals using the second receiver LNA 56, and deliver the amplified band B receive signals to a second band B receive node RX_B1 for further processing, for example, by baseband circuitry (not shown).
The filtering circuitry 38 includes a first duplexer 58A, a second duplexer 58B, a first receiver filter 60A, and a second receiver filter 60B. The first duplexer 58A passes band A transmit signals between the first power amplifier 46 and the front end switching circuitry 36 and passes band A receive signals between the front end switching circuitry 36 and the first LNA 48, while attenuating signals outside of the respective transmit and receive signal bands. Similarly, the second duplexer 58B passes band B transmit signals between the second power amplifier 50 and the front end switching circuitry 36 and passes band B receive signals between the front end switching circuitry 36 and the second LNA 52, while attenuating signals outside of the respective transmit and receive signal bands. The first receiver filter 60A passes band A receive signals between the front end switching circuitry 36 and the first receiver LNA 54, while attenuating other signals. Similarly, the second receiver filter 60B passes band B receive signals between the front end switching circuitry 36 and the second receiver LNA 56, while attenuating other signals.
The front end switching circuitry 36 includes band selection circuitry 62, antenna swapping circuitry 64, and switching control circuitry 66. The band selection circuitry 62 includes low-band selection circuitry 68 and mid/high-band selection circuitry 70 for each one of the first antenna 32A and the second antenna 32B. Specifically, the band selection circuitry 62 includes first low-band band selection circuitry 68A coupled to the first antenna 32A through the first diplexer 34A, first mid/high-band selection circuitry 70A coupled to the first antenna 32A through the first diplexer 34A, second low-band selection circuitry 68B coupled to the second antenna 32B through the second diplexer 34B, and second mid/high-band selection circuitry 70B coupled to the second antenna 32B through the second diplexer 34B. Each one of the diplexers 34 are configured to pass low-band signals between the connected low-band selection circuitry 68 and the connected one of the antennas 32, pass mid/high-band signals between the connected mid/high-band selection circuitry 70 and the connected one of the antennas 32, and attenuate signals outside of the respective low and mid/high bands while providing isolation between the connected low-band selection circuitry 68 and the mid/high-band selection circuitry 70. The band selection circuitry 62 is configured to place one or more modules in the transceiver circuitry 40 in contact with the first antenna 32A or the second antenna 32B in order to transmit and receive signals about the operating bands associated with the one or more transceiver modules 42.
The antenna swapping circuitry 64 is coupled between the transceiver circuitry 40 and the band selection circuitry 62, and is configured to swap the antenna 32 presented to the first duplexer 60A, the second duplexer 60B, the first receiver filter 60A, and the second receiver filter 60B. As will be appreciated by those of ordinary skill in the art, the antenna swapping circuitry 64 may swap antennas 32 between the respective filtering elements in the filtering circuitry 38 in order ensure that signals are transmitted from either the first transceiver module 42A or the second transceiver module 42B using the one of the antennas 32 with the most favorable transmission characteristics at the time.
The switching control circuitry 66 operates the band selection circuitry 62 and the antenna swapping circuitry 64. In a first operating mode of the front end switching circuitry 36, the switching control circuitry 66 operates the band selection circuitry 62 and the antenna swapping circuitry 64 to place the first transceiver module 42A and the second transceiver module 42B in contact with the first antenna 32A through the first duplexer 58A and the second duplexer 58B, respectively, and place the first receiver module 44A and the second receiver module 44B in contact with the second antenna 32B through the first receiver filter 60A and the second receiver filter 60B, respectively. In this configuration, the conventional front end circuitry 30 may simultaneously transmit band A signals while receiving band A signals and band B signals from the first antenna 32A, and simultaneously receive band A signals and band B signals from the second antenna 32B. Alternatively in this configuration, the conventional front end circuitry 30 may simultaneously transmit band B signals while receiving band A and band B signals from the first antenna 32A, and simultaneously receive band A signals and band B signals from the second antenna 32B.
In a second operating mode of the front end switching circuitry 36, the switching control circuitry 66 operates the band selection circuitry 62 and the antenna swapping circuitry 64 to place the first transceiver module 42A and the second transceiver module 42B in contact with the second antenna 32B through the first duplexer 58A and the second duplexer 58B, respectively, and place the first receiver module 44A and the second receiver module 44B in contact with the first antenna 32A through the first receiver filter 60A and the second receiver filter 60B, respectively. In this configuration, the conventional front end circuitry 30 may simultaneously transmit band A signals while receiving band A signals and band B signals from the second antenna 32B, and simultaneously receive band A signals and band B signals from the first antenna 32A. Alternatively in this configuration, the conventional front end circuitry 30 may simultaneously transmit band B signals while receiving band A signals and band B signals from the second antenna 32B, and simultaneously receiving band A signals and band B signals from the first antenna 32A.
Although capable of operating in one or more carrier aggregation configurations, the conventional front end circuitry 30 generally suffers from poor efficiency. As discussed above, both the first transceiver module 42A and the second transceiver module 42B are connected to either the first antenna 32A or the second antenna 32B, depending on which antenna is used for the transmission of signals, at any given time. Accordingly, at least one of the first antenna 32A or the second antenna 32B is always loaded by at least a quadplexer, which is formed from the combination of the first duplexer 58A and the second duplexer 58B. The relatively large load associated with the combination of the first duplexer 58A and the second duplexer 58B results in excessive insertion loss in the conventional front end circuitry 30, thereby degrading the efficiency of a mobile terminal in which the conventional front end circuitry 30 is incorporated.
As shown in FIG. 3, each filtering element in the filtering circuitry 38 is tunable, such that the filter response of the various filtering elements can be tuned to isolate a signal or signals about a given frequency range. In intra-band non-contiguous carrier aggregation applications, using tunable filtering elements in the conventional front end circuitry 30 may be problematic, as the bandwidth of the pass band of each one of the filtering elements may need to accommodate at least an entire operating band (i.e., the required pass-band of each filtering element could be as large as 80 MHz in some cases). In other words, because only two antennas 32 are provided in the conventional front end circuitry 30, and because only one transceiver module 42 and one receiver module 44 are provided for each operating band in the conventional front end circuitry 30, the filtering element associated with each one transceiver module 42 or receiver module 44 must be capable of passing signals about the entire operating band to its associated transceiver module 42 or receiver module 44 when the conventional front end circuitry 30 is operating in an intra-band non-contiguous carrier aggregation configuration. That is, since intra-band non-contiguous carrier aggregation may involve aggregating bandwidth about portions of an operating band located at separate ends of the operating band, each one of the filtering elements in the filtering circuitry 38 must be capable of passing these signals to the appropriate transceiver module 42 or receiver module 44 in the transceiver circuitry 40 in order to properly operate in such a configuration. As will be appreciated by those of ordinary skill in the art, tunable filtering elements including a large pass-band are difficult to design and manufacture, often adding cost and complexity to the front end circuitry in which they are incorporated. Further, such tunable filtering elements may introduce a significant amount of insertion loss as a result of the required pass-band, thereby degrading the performance of the conventional front end circuitry 30. Accordingly, there is a need for front end circuitry that is capable of operating in a variety of carrier aggregation configurations while also maintaining the efficiency and performance of the front end circuitry.